The efficiency of power generation, transmission and distribution equipment is improved when it is operated at or near unity power factor. The least expensive way to achieve unity power factor is with the application of power factor correction capacitors. These capacitors provide a static source of leading reactive current and can be installed close to the load. Capacitors can be pole-mounted in racks or used in electrical substations in factory-assembled blocks.
Capacitors consist of a tank structure which confines a dielectric around an electrical component through which electrical current flows. The capacitor tank is rectangular in shape and has two sets of elongated walls, a bottom wall and a top wall. The walls may be formed from stainless steel and are usually protected with an enamel-like finish to resist corrosion and to facilitate dissipation of whatever heat is generated within the capacitor. For convenience in handling and installation, two of the opposite side walls are provided with hangers. Hangers allow the capacitors to be bolted to mounting structures (FIG. 1).
In the past, capacitor hangers have been connected to the capacitor tank wall by a welding process such as tungsten inert gas (TIG) welding wherein an arc plasma from a tungsten electrode radiates heat to melt the work surface in a protective atmosphere of inert gas. TIG welding requires temperatures of about 2300.degree. F. to melt the tank and hanger metals and cause them to fuse together. Because of the heat involved in the TIG welding process and the relatively thin wall thickness (0.040-0.050") of the capacitor tank, the structural integrity of the capacitor tank wall can be compromised by the welding. The resulting change in the metallurgical structure of the tank metal can cause cracks. Since dielectric fluid is sealed in the capacitor tank, a crack can render the entire component useless. To compound the problem, the cracks often do not appear until the capacitors are transported and installed in the field.
There is a need therefore, for a capacitor tank and hanger assembly wherein the hanger can be connected to the capacitor tank without causing cracks in the capacitor tank wall.